Superaerophobic Hydrogels for Diaphragm Modification to Suppress Gas Crossover in Alkaline Water Electrolyzers

Abstract

Water electrolysis enables the sustainable production of hydrogen without greenhouse gas emissions, thereby supporting energy supply-demand balancing in decarbonized energy systems. Among low-temperature electrolyzer technologies, alkaline water electrolyzer (AWE) is the most mature owing to its proven durability and reliance on inexpensive materials.However, AWEs still face safety concerns due to hydrogen explosion risks arising from gas crossover through porous diaphragms. Suppressing gas crossover is therefore essential for the safe and scalable deployment of AWE systems. Herein, we present a strategy to control diaphragm wettability via superaerophobic polyvinyl alcohol (PVA) hydrogel coatings that mitigate gas crossover. Penetrated oxygen reduction reaction (ORR) analysis, dissolved oxygen quantification, and oxygen purity evaluation consistently confirmed a reduced gas crossover rate, attributed to the hydrogel's superaerophobicity. In situ visualization further demonstrated rapid bubble detachment from the hydrogel-coated surface, preventing pressure buildup and suppressing bulk gas penetration. Overall, this study introduces a simple, energy-efficient diaphragm modification strategy that directly addresses a key safety challenge in AWE. By improving gas management without compromising electrochemical performance, this approach offers a practical pathway toward safer and more reliable alkaline water electrolysis for industrial hydrogen production.